1. Field of the Invention
The present invention relates to an upright-pin-joined resin substrate having pins serving as input/output terminals arranged in a standing posture, a method of producing the upright-pin-joined resin substrate, a pin serving as an input/output terminal provided in the upright-pin-joined resin substrate, and a method of producing the pin.
2. Description of the Related Art
Conventionally, an upright-pin-joined resin substrate has been known; i.e., a resin substrate having pins which serve as input/output terminals. The pins are provided on a resin substrate formed from a resin or a resin-containing composite material, and are arranged in a standing posture.
An example of such an upright-pin-joined resin substrate is shown in FIG. 9, which is a partially enlarged cross-sectional view of an upright-pin-joined substrate 201. The upright-pin-joined resin substrate 201 includes a resin substrate 203 having a generally rectangular plate-like shape, and a number of pins 221 arranged on the substrate in a standing posture.
The resin substrate 203 includes a resin insulating layer 205 having wiring layers (not shown) formed in the interior and on the surface thereof, and a number of pin pads 209 exposed through a solder resist layer 207 on the a main plane 203A side (on the upper side in FIG. 9).
The pin 221 is formed of a material such as 194 Alloy (Cu— (2.1-2.6 wt. %)Fe— (0.05-0.2 wt. %)Zn— (0.015-0.15 wt. %) P), and includes a generally cylindrical shaft portion 221A and a generally disk-like enlarged-diameter portion 221B joined to the surface of one of the pin pads 209. The entirety of the enlarged-diameter portion 221B and a part of the shaft portion 221A connecting with the enlarged-diameter portion 221B are joined to the pin pad 209 by means of a solder HD, to thereby fixedly join the pin 221 to the resin substrate 203. The material used for forming the pin 221 is not necessarily limited to 194 Alloy, and examples of the material include copper materials such as pure copper, phosphor bronze, nickel silver, and beryllium copper, and ferrous materials such as kovar (Fe—Ni—Co alloy) and 42 Alloy (Fe-42 wt. % Ni alloy).
3. Problems to be Solved by the Invention
However, when stress is applied to the pin 221 as is the case where the pin 221 is pulled, even though the stress is comparatively small, the aforementioned upright-pin-joined resin substrate 201 may fracture at the solder portion HD between the pin 221 and the pin pad 209 or a scoop portion of the resin substrate 203 (resin insulating layer 205) may be removed. The reason for the fracture is considered to be as follows. The pin 221, having high hardness, cannot absorb stress generated due to soldering or stress applied thereto during a tensile test or other processes. If the stress is concentrated for some reason, the solder HD between the pin 221 and the pin pad 209 or the resin substrate 203 (resin insulating layer 205) fractures prior to occurrence of a fracture in the shaft portion 221A of the pin 221.
When such pins 221 joined to a substrate are subjected to a tensile test, some exhibit such a high connection strength such that joining is maintained until the shaft portion 221A of each hard pin 221 fractures, whereas others exhibit exceptionally poor connection strength. Thus, variation in connection strength among the pins is rather large, resulting in joining of poor reliability.